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An analytical study of the directional behavior of a tractor-semitrailer vehicle with steered trailer axles is discussed. The model was used to determine the influence of design parameters and steering inputs on the directional behavior of the tractor-semitrailer combination with steered trailer axles. Results obtained from the computer simulation study indicated that the maneuverability of an articulated vehicle with steered trailer axles was improved. The influence of fifth-wheel location with respect to tractor cg on the vehicle directional behavior in a steady-state turning maneuver was also investigated. Fifth-wheel locations near the tractor cg were most effective in reducing the angles of sideslip and articulation.

Recent interest in improving vehicle handling performance has concentrated not only upon achieving maximum acceleration or braking ability of the motor vehicle, but also upon maintenance of high lateral stability during acceleration or braking. This study examines the influence of tire traction and vehicle characteristics on the directional behavior of an automobile undergoing maneuvers requiring combined longitudinal and lateral tire forces. The vehicle model considered in this analysis consists of ten degrees of freedom, including wheel rotational dynamics and steering system characteristics. The equations of motion for the sprung and unsprung masses have been derived using Lagrange's special equations for quasi-coordinates. The analysis includes nonlinear tire traction characteristics which expresses the longitudinal and lateral tire shear force components as analytical functions of several parameters.

This paper discusses the computer simulation of a road-vehicle directional response to fixed-control steering inputs using a general purpose simulation language, ACSL. The equations of motion are derived to evaluate the vehicle directional behavior in terms of sideslip angle, yawing velocity gain, and path curvature gain. Computer simulations have been performed to examine the influence of tire lateral stiffnesses, load distribution on front and rear axles, and forward speed on vehicle directional response, in particular on the vehicle turning geometry.

For mathematical modeling and analysis of vehicle dynamic performance, a variety of inertial properties are of significance. These include: mass; center of gravity location; yaw, pitch, and roll moments of inertia; and the location of the principal axes of inertia. The large size of most commercial highway vehicles can lead to significant problems in determining, either by computations or by measurements, all of the inertial properties appearing in the mathematical description of a vehicle system. In this paper, new techniques in the measurements of the inertial properties of a cabin of a large commercial highway vehicle are developed and discussed. The specific testing techniques which are employed are extensively described. These measurement techniques are simple and inexpensive, but the resulting information may be of great value to the vehicle dynamics researchers.